Printed circuit boards are commonly used in electronic devices such as instruments, computers, telecommunication equipment and consumer electronic products. Typically, an engineer will design a printed circuit board to carry the types of components necessary to implement the desired electronic function and to fit in the space available for the board. Consequently, each printed circuit board typically is custom designed. To design a custom printed circuit board is expensive, takes time and requires the fabrication of prototype printed circuit boards. If errors are found in the prototypes, then the printed circuit board must be redesigned. Such a process often delays the planned introduction of a new product.